Calculating Distance for Jumping off a Slope at 45°

[borovecm]

Homework Statement

I have to calculate disctance that body(for example a jumper) that jumps of a slope at 45 degrees with initial speed of 20 m/s and under 15 degrees.

Homework Equations

x=Vox * t
y=Voy*t - 1/2*g*t*t

y=ax + b, b=0 => y=ax
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The Attempt at a Solution

I don't know where to start. I can solve a simillar example where body has been shot from a building with a certain initial speed and under under 30°. It is simillar to this picture, but here it is difference that we shoot from a slope and we don't know at what height we only know that slope is placed under 45° with a surface.

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[hage567]

What have you tried? Where are you stuck? Show us your work so far.